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E. Hansy-Staudigl:
"Nonlinear modeling and analysis of thin dielectric elastomer structures as electro-elastic material bodies and surfaces";
Supervisor, Reviewer: M. Krommer, H Irschik, H. Altenbach; Institut für Mechanik und Mechatronik, 2020; oral examination: 2020-06.

Soft materials, which deform under an electrical stimulation pose exciting new options for a technologically new generation of load bearing mechanical devices such as soft robots, assistant devices or solid state aircrafts. Promising candidates for such soft, smart materials are dielectric elastomers (DEs), a special type of electroactive polymers (EAPs). An intriguing property of DEs is the circumstance that they work the better the smaller the thickness gets. Taking advantage of this fact gives rise to the typical thin application designs for which a structural mechanics approach to the modeling of dielectric elastomer plates and shells as a material surface applies.Modeling dielectric elastomers vouch for multiple challenges as there are large deformations, hyperelasticity and multiple levels of electro-mechanical couplings by means of electrostatic forces as well as higher order effects such as piezoelectricity and electrostriction. Taking the electro-elastic coupled theory into the center of this thesis, the governing equations get gradually extended from the incorporation of electrostatic forces to higher order effects by means of electrostriction. To this end, the constitutive relations are step by step extended from the three dimensional to the structural level and multiple multiplicative decompositions of the deformation gradient tensor enable an increased coupling between the mechanical and the electrical fields.A direct approach for modeling plates and shells as a material surface enables the elegant development of a thorough structural theory. In particular, contradiction free two dimensional constitutive relations for a hyperelastic plate, with separate membrane and bending parts comprise a novelty and offer great physical insight. Numerical studies on different example problems confirm the validity of the developed models in comparison to three dimensional results as well as in comparison to different approaches found in literature.

Structure Mechanics; Electro-Elasticity; Dielectric Elastomers; Electrostriction; Multiplicative Decompsoition

http://dx.doi.org/10.34726/hss.2020.73700